Table 1.

Description of the included studies.

Author	Year	Journal	Study Design	Intervention Population	Intervention	Outcome
Azaripour et al. [22]	2015	BMC Oral Health	Cross-sectional study	100 participants; 50 with invisible orthodontics, 50 with fixed orthodontics.	Patient home hygiene protocol	Gingival index; sulcus bleeding index; approximal plaque index
Caccianiga et al. [22]	2022	Healthcare	Cross-sectional observational study	50 participants; 25 with invisible orthodontics, 25 with fixed orthodontics.	Patient home hygiene protocol	Qualitative microbiological analysis of oral flora: pathogenic or non-pathogenic. Plaque assessment by SEM
Chhibber et al. [19]	2018	American Journal of Orthodontics and Dentofacial Orthopedics	Randomized control trial (RCT)	61 participants; 24 with invisible orthodontics, 37 with fixed orthodontics (17 with self-ligating attachments and 20 with elastomeric attachments).	Patient home hygiene protocol	Plaque index; gingival index; papillary bleeding index
Levrini et al. [25]	2013	Cumhuriyet Dent J	Randomized control trial (RCT)	30 participants; 10 with invisible orthodontics, 10 with fixed orthodontics, 10 without orthodontics (control group).	Patient home hygiene protocol	Plaque index; probing pocket depth; bleeding on probing; microbiological analysis through real-time PCR evaluation
Levrini et al. [26]	2015	European Journal of Dentistry	Randomized control trial (RCT)	77 participants; 32 with invisible orthodontics, 35 with fixed orthodontics, 10 without orthodontics (control group).	Patient home hygiene protocol	Plaque index; probing pocket depth; bleeding on probing; microbiological analysis through real-time PCR evaluation
Levrini et al. [18]	2015	Clinical, Cosmetic and Investigational Dentistry	Crossover study	36 aligners (3 aligners for 12 patients).	Orthodontic devices home hygiene protocol	Microbiological analysis: evaluation of the amount of plaque by SEM
Levrini et al. [16]	2016	International Journal of Dentistry	Crossover study	36 aligners (3 aligners for 12 patients).	Orthodontic devices home hygiene protocol	Microbiological analysis: evaluation of bacterial concentration by analyzing the amount of ATP using a bioluminometer. Bacterial concentration is expressed in RLUs (relative light units)
Lombardo et al. [17]	2017	Progress in Orthodontics	Crossover study	45 aligners (9 aligners for 5 patients).	Orthodontic devices home hygiene protocol	Microbiological analysis: observation of the presence of biofilms by scanning electron microscopy (SEM). The measurement is carried out with a Grey scale
Sfondrini et al. [21]	2021	Applied sciences	Randomized control trial (RCT)	40 participants; 20 with invisible orthodontics, 20 without orthodontics (control group).	Patient home hygiene protocol	Plaque index; bleeding on probing; probing pocket depth; quantitative and qualitative microbiological analysis of the flora through real-time PCR analysis
Shpack et al. [15]	2014	Angle Orthodontist	Crossover study	132 aligners (12 aligners for 11 patients).	Orthodontic devices home hygiene protocol	Microbiological analysis: evaluation of biofilm adhesion measured by photodensitometer
Zhao et al. [20]	2020	Oral Diseases	Cross-sectional study	25 with invisible orthodontics.	Patient home hygiene protocol	Plaque index; probing pocket depth; bleeding on probing